Prior art trough shaped solar concentrators have been based on either curved parabolic reflectors or linear flat strip reflectors arranged in a Fresnel configuration where each strip reflector was mounted at an angle to reflect the sunlight falling on it to the central line focus of the trough. When a receiving element designed to receive the concentrated solar energy and convert it to another type of energy is placed at the line focus of the trough concentrator, the preferred embodiment of most of these concentrators, a concentrating solar collector is achieved. In prior art trough shaped solar collectors the receiving element has been placed at the very top edge, just within the aperture, trough mouth, of the trough, or above the trough opening. While this placement of the receiving element works, greater thermal efficiency, for a receiver designed to convert the solar energy to thermal energy, can be achieved by locating the receiver element further down inside the boundaries of the trough reflector.